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CaTiO3 induced ferroelectric phase coexistence and low temperature dielectric relaxation in BaTiO3–BaZrO3 ceramics
(2018-05-01)
Sutapun, Manoon
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Charoonsuk, Thitirat
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Kolodiazhnyi, Taras
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Vittayakorn, Naratip
The series of 0.86BaTiO<inf>3</inf>–(0.14−x)BaZrO<inf>3</inf>–xCaTiO<inf>3</inf> (abbreviated as BT–BZ–xCT) ceramics with 0.03 ≤ x ≤ 0.11 were studied to obtain high piezoelectric properties. Rietveld refinement analysis indicated that the BT–BZ–CT compositions follow a gradual rhombohedral (R) → orthorhombic (O) + R → O + tetragonal (T) → T phase transformation with increasing x. Clear evidence of the series of ferroelectric phase transitions was also found in the dielectric results. The R-O and O-T transition temperature shifted close to ambient temperature, while the Curie temperature slightly increased with increasing x. In addition to the dielectric loss peaks associated with the structural phase transitions, a broad low-temperature dielectric loss peak was detected in the R phase at T = 90-150 K. This dielectric relaxation was attributed to the domain wall freezing and fits well to the Vogel-Fulcher model with activation energy E<inf>a</inf> ≈ 60-300 meV and freezing temperature T<inf>VF</inf> ≈ 75-140 K. High piezoelectric strain coefficient (d<inf>33</inf>*) of about 1030 pm/V at 10 kV was achieved at x = 0.07, and a high Curie temperature (T<inf>C</inf>) was maintained at about 375 K.
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Phase transition, dielectric and piezoelectric properties of lead-free piezoelectric (K1/2Na1/2)NbO3 - Bi(Zn2/3Nb1/3)O3 ceramics
(2016-01-02)
Sutapun, Manoon
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Muanghlua, Rangson
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Vittayakorn, Naratip
The lead-free piezoelectric ceramics on the binary system of (1-x)(K<inf>1/2</inf>Na<inf>1/2</inf>)NbO<inf>3</inf>-xBi(Zn<inf>2/3</inf>Nb<inf>1/3</inf>)O<inf>3</inf> [(1-x)KNN-xBZnN]; x = 0.01-0.10 were fabricated by the solid state reaction method. The structure and phase transition were determined by X-ray diffraction.The results of XRD patterns suggested that Bi(Zn<inf>2/3</inf>Nb<inf>1/3</inf>)O<inf>3</inf> completely diffuse into the (K<inf>1/2</inf>Na<inf>1/2</inf>)NbO<inf>3</inf> lattices to form a solid solution. The crystal structure was in an orthorhombic phase for x ≤ 0.01. When reaching 0.01 < x ≤ 0.07, crystal structure became a rhombohedral phase and transformed to a pseudo-cubic structure for x > 0.07. The dielectric data shows that the amount of Bi(Zn<inf>2/3</inf>Nb<inf>1/3</inf>)O<inf>3</inf> added in the (K<inf>1/2</inf>Na<inf>1/2</inf>)NbO<inf>3</inf> decreases the ferroelectric - paraelectric transition temperature progressively. Furthermore, optimum piezoelectric and ferroelectric properties were observed at the composition, x = 0.01: effective piezoelectric coefficients (d<inf>33</inf>) = 498 pm/V, remanent polarization (P<inf>r</inf>) = 23.3 μC/cm<sup>2</sup>, coercive field (E<inf>c</inf>) = 14 kV/cm, maximum strain (Sma<inf>x</inf>) = 0.3% and Curie temperature (T<inf>C</inf>) = 380°C. The results of this study show that KNN with a small amount of Bi(Zn<inf>2/3</inf>Nb<inf>1/3</inf>)O<inf>3</inf> (x = 0.01) can be one of lead-free piezoelectric ceramic candidate.
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Dielectric, ferroelectric and piezoelectric properties of the lead free 0.9BaTiO3-(0.1- x)Bi0.5Na0.5TiO3- x Bi(Mg0.5Ti0.5)O3 solid solution
(2016-01-02)
Mayamae, Jitkasem
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Sukkha, Usa
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Niemchareon, Surasak
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Muanghlua, Rangson
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Vittayakorn, Naratip
Solid solution of 0.9BaTiO<inf>3</inf>-(0.1-x)Bi<inf>0.5</inf>Na<inf>0.5</inf>TiO<inf>3</inf>-xBi(Mg<inf>0.5</inf>Ti<inf>0.5</inf>)O<inf>3</inf> (BT-BNT-xBMT) system, where x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10, was synthesized by the solid state reaction. Dense BT-BNT-xBMT ceramics were obtained by sintering at 1,150-1,250C for 4 h. The effect of BMT on crystal structure and electrical property of BT-BNT ceramics was investigated as a function of composition, x, using X-ray diffraction, dielectric spectroscopy, hysteresis and strain measurements. The crystal structure of solid solution BT-BNT-xBMT, where x = 0.00-0.10, successively transforms from tetragonal to pseudocubic symmetry, with increased BMT concentration. Temperature dependence of dielectric constant (ε<inf>r</inf>) and dielectric loss (tanδ) for BT-BNT-xBMT at various frequencies showed that phase transition of ceramics changed from ferroelectric to relaxor-like behavior as BMT content increased. Furthermore, remanent polarization (P<inf>r</inf>), coercive field (E<inf>c</inf>) and the normalized strain (d<inf>33</inf>∗) of BT-BNT-xBMT ceramics tend to decrease with increasing BMT concentration.
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Effect of BiYbO3 Addition with a Small Tolerance Factor on Ferroelectricity and TC in PbZrO3 Ceramics
(2015-10-08)
Sukkha, Usa
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Niemcharoen, Surasak
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Vittayakorn, Naratip
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Guo, Ruyan
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Bhalla, Amar S.
Perovskite (Pb(1-3x/2) Bi<inf>x</inf>)(Zr(1-3<inf>x/4</inf>) Yb<inf>x</inf>)O<inf>3</inf> (PZ-BY) ceramics, where x = 0.01-0.10, were synthesized by conventional solid state reaction. The effect of BiYbO<inf>3</inf> on crystal structure, phase transitions and electrical properties was studied as a function of composition. The X-ray diffraction (XRD) result indicated that the perovskite structure with orthorhombic symmetry was a major phase for all samples. The pyrochlore phase, identified as Yb<inf>0.2</inf>Zr<inf>0.8</inf>O<inf>1.9</inf>, coexists in PZ-BY ceramics. The influence of instability and a small tolerance factor (t) and the average electronegativity difference () of pure BY on phase formation of PZ-BY ceramic has been discussed. Furthermore, it was found that adding small tolerance factor BiYbO<inf>3</inf> compound can stabilize the antiferroelectric (AFE) phase of PZ solid solutions and decreasing t of solid solution can enhance Curie temperature of PZ.

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